The statutory basis
Yes. A solo rider may use an HOV lane.RCW 46.61.165 names motorcycles as their own eligible class, so you do not need a passenger to qualify.
RCW 46.61.165 authorizes state and local authorities to reserve lanes for high occupancy vehicles, and the eligible classes it lists are public transportation vehicles, motorcycles, and private motor vehicles carrying no fewer than a specified number of passengers.
Motorcycles appear as their own category. That is why a solo rider qualifies where a solo driver does not.
What it does not get you
HOV access is not a general exemption from traffic law, and riders sometimes stretch it.
- It does not permit riding on the shoulder.
- It does not permit splitting or filtering between lanes, which stays prohibited under RCW 46.61.608.
- It does not override posted access restrictions or the solid double line marking an HOV lane. Enter and exit where the striping allows.
- Express toll lanes are a separate system with their own rules and, in some corridors, their own transponder requirements. Read the signage for the corridor you are on.
Using it well
The HOV lane is usually the fastest lane, which makes it the lane with the largest speed differential against everything beside you. That cuts both ways for a motorcycle.
Two habits worth building. First, watch for the car that decides to dive across the line into the HOV lane without looking, because that maneuver is the classic HOV-lane crash and you are the least visible thing in it. Second, be deliberate about your own entries and exits rather than treating the lane as somewhere to hide from congestion.
On a wet Puget Sound commute the lane also carries less traffic, which means less rubber laid down and, right after the first rain, a slightly different grip picture than the lanes beside it.